Cell culture technology has advanced significantly over the last few decades and has contributed immensely in therapeutic applications, clinical studies, pharmaceutical research and development, and the bioprocess industry by expanding various cell lines and synthesizing different biomolecules of interest. To meet an increasing demand of therapeutic protein candidates (such as monoclonal antibodies) or viable cells (such as mammalian cell lines) for therapeutic applications, large scale manufacturing facilities and high throughput technological developments for culturing large quantities of cells are highly desirable.
Bioreactors have long been practiced as the preferred scale-up method for cell expansion in bioprocess industry. Use of a seed train for cell expansion from a cryo-preserved inoculum is a significant process step to initiate a large-scale manufacturing campaign. For manufacturing biotherapeutics, maintaining a desired quality of cells or biomolecules is a key requirement. A seed train expansion is significant since the use of cryopreserved inoculum can directly be used for expansion of cells, which may ensure a desired quality.
In a typical seed train expansion process, cells are initially cultured from a cryopreserved small inoculum (e.g., 1-2 mL). The cryopreserved cells are thawed and seeded to culture vessels, such as T-flasks or spinner flasks and cultured by adding culture media under controlled incubation. To achieve a desired cell number, the cells are usually distributed in multiple culture vessels, followed by transferring to larger culture vessels with additional growth medium. The process of transferring cells into multiple vessels, adding growth medium and culturing cells are repeated until a determined cell mass is obtained for large scale production, and finally the cells are seeded to a bioreactor, such as Cellbag™ for WAVE Bioreactor™ or an Xcellerex™ for XDR stirred-tank bioreactor with single-use bag. However, the current seed train expansion process is disadvantageous as the process requires labor intensive and complex manual handling and generates a risk of contamination when using multiple culture vessels and repeated inoculum transfer. In addition, the lack of control of different parameters, such as pH or dissolved oxygen during scale-up may result in batch-wise variation of cell expansion. Further, the existing process and the set-up for the seed train expansion from a cryo-preserved cell sample requires a well trained personnel.
In bioreactor, change in volume of a media in a bioreactor vessel introduces changes on internal parameters of a bioreactor, such as pH, DO or temperature, the change may be compensated by having a vessel geometry that compensates for media volume increase and thus a simple more robust controller can be used to maintain the system parameters. Due to large volume change, control performance of standard controllers, such as a proportional-integral-derivative (PID) controller may not be sufficient. Therefore, there is a need to develop a robust system and process for seed train expansion at different scales that provides an optimization of parameters and culture conditions that achieve requisite productivity and desired quality with minimum human intervention and ensures a smooth scale-up.